Empirical Model for Shear Strength of Artificial Rock Containing a Single Nonpersistent Joint

Abstract

This paper proposes an empirical equation to evaluate the shear strength of rock mass with nonpersistent joints. A novel specimen preparation method is proposed and is used to created plaster specimens containing nonpersistent joints. Utilizing the proposed method, it is possible to create specimens with nonpersistent closed joints with different roughness levels along different directions. The normal stress applied to embedded nonpersistent joints is the key factor for estimating the joint friction contribution to the shear strength of rock mass with the joints. An analytical equation and an experimental approach are proposed to calculate the normal stress applied to the nonpersistent joints. Seemingly good agreement was found between the normal stress values obtained using the analytical equation and those measured by the experimental approach. To study the effects of four influential parameters, namely rock bridge ratio, material strength, joint roughness, and normal stress, on the shear strength of specimens with a single nonpersistent joint, an experimental layout was designed based on the Taguchi method. The results of the extensive experimental work were then expressed in terms of an empirical equation to calculate the shear strength of specimens embedding a single nonpersistent joint.